From: Jim Gilmore (jgilmore@ptd.net)
Date: Sun Oct 03 2004 - 09:41:37 PDT
Dick wrote:
> My M151A1 starts fine. It runs for about 20 minutes, then quits. I let it sit for about 10 minutes, then re-start it with no problem. It runs for about 3 minutes, quits again. I can repeat this many times. If I let it sit over night, the same pattern.
There are two types of fuel tank caps used in the M-series vehicles. Vented and non-vented. Both will interchange and look alike. In addition, some caps have a valve inside them that can be turned to make it non-vented or vented.
If you are using a non-vented cap or the valve is closed eventually the vacuum in the tank will be greater than the fuel pumps and you will actually run out of fuel in the carb. After some minutes, the vacuum in the tank will subside and your pump will be able to deliver enough fuel to the carb.
When your motor quits, open the gas cap. if you hear air going into the tank, you have the wrong cap or the valve is closed.
As another test, try driving the vehicle with the gas cap loose and see if this corrects the problem. If so, replace the cap with the correct one.
Also note: There are two different fuel systems for the M-151-A2.
"Clean Air" systems and pre-"Clean Air" systems. The components, Carb, fuel tank, fuel tank cap are specific to each system. Use of components from one on the other will cause problems in driveability. The fuel tank cap from the "Clean Air" system should not be used with Pre-"Clean Air" fuel tank.
Jim Gilmore
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